The present invention relates to apparatus and method for displaying weather information. More specifically, it relates to apparatus and method for displaying weather information obtained from an airborne weather radar.
Aircraft equipped with weather radars are able to collect information concerning weather conditions in the airspace in front of the aircraft. The weather radars generally include at least a transmitter, a receiver, an antenna and a display. The weather radar examines a weather cell, which comprises a limited area of space in front of the aircraft, by transmitting energy from the transmitter through the antenna along the line in which the antenna is pointing. The position of the antenna is incrementally stepped so that energy is transmitted throughout the weather cell during a scan. If a weather disturbance, such as a rain storm, is in the weather cell then a portion of the transmitted energy will be reflected. The reflected energy is collected by the antenna and fed to the receiver. The weather information is derived from the reflected energy and then displayed to a pilot to aid in the navigation of the aircraft.
The antenna usually fits into the front cone of the aircraft and, therefore, is limited to the size of the cone. In smaller commuter type aircraft, for example, antennas having diameters of 8 inches, 10 inches or 12 inches are common. Antennas of this size, however, transmit a beam that widens as the beam travels away from the aircraft. These beams, if visible, typically would look conical. As a result, energy is reflected when the fringe areas of the conical transmitted beams first encounter a weather disturbance as well as when they leave the weather disturbance. Since the weather radar thinks the antenna is pointing along the center of the conical beam and, therefore, does not expect returns resulting from the fringe areas of the transmitted beam, the resulting weather information is distorted. The distorted weather information is then displayed to a pilot, a less than desirable situation.